Electromagnetic track brake for a railway vehicle

ABSTRACT

An electromagnetic track brake for a railway vehicle comprises an elongate brake energizing coil for energizing a plurality of U-shaped braking shoes mounted in a row on a rigid frame. To improve transmission of braking reaction forces from the shoes to the vehicle each shoe is moved downwards individually relative to the frame against spring bias. A tie rod extends along a lower branch of the coil engaging each of the braking shoes for the transmission of braking forces from the shoes to the tie rod. A cylindrical rod rigidly coupled to the frame is operably connected to the end of the tie rod to take up the braking reaction forces transmitted to the tie rod.

TECHNICAL FIELD

This invention relates to an electromagnetic track brake to be mountedon a railway vehicle for cooperation with a rail and comprising anelongate brake energizing coil, a rigid frame, and a plurality ofU-shaped braking shoes mounted in a row in the frame around the lowerbranch of the coil and having braking surfaces disposed beneath the coilto frictionally engage the rail when the coil is energized.

BACKGROUND ART

Electromagnetic track brakes of this type are well known in the art.Typical for the prior art brakes is that the frame for the elongatebrake energizing coil is suspended from the vehicle, viz. the bogie ortruck frame, over the rail in such a way that the braking force istransmitted from the braking shoes to the vehicle over the coil and itsnormally enclosing frame. Accordingly, the coil frame partakes in theforce transmission between the braking shoes and the vehicle andtherefore has to be of a sturdy and reliable construction. Moreover, thetransmission of braking forces over the coil frame provides a lessfavourable taking-up of the torque and forces involved, so that unevenwear of the braking shoes may occur.

DISCLOSURE OF INVENTION

The disadvantages mentioned above are obviated by the invention whichprovides an electromagnetic track brake of the type referred to, inwhich each braking shoe is individually movable in a vertical directionrelative to the frame and is lightly biased upwards towards a restposition, preferably by means of springs.

Further, the track brake has a tie rod extending along the lower branchof the coil and a covering therefor and engaging each of the brakingshoes for the transmission of braking reaction forces from the shoes tothe tie rod, and also has means rigid with the frame of the vehicle andoperatively connected to the end of said tie rod to take up the brakingreaction forces transmitted to the tie rod.

In this way the coil will be relieved from the transmission of thebraking reaction forces and accordingly can be of a simple and cheapconstruction. No normal coil frame will be required, only a protectivecovering.

A further advantage is that the mounting of the coil to the vehicle isfacilitated due to the fact that no braking reaction forces are carriedover such mounting. Preferably, the brake is suspended from the journalboxes of the vehicle.

The means operatively connected to one end of the tie rod can easily beintegrated with the bogie or truck frame of the vehicle and preferablyconsists of a sturdy bracket supporting a substantially vertical rodwhich is engaged by an eye at the end of the tie rod, said eye beingdisplaceable along the rod.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below, reference beingmade to the accompanying drawings in which

FIG. 1 is a side view, partly a longitudinal cross-sectional view, of anelectromagnetic track brake according to the invention,

FIG. 2 is a cross-sectional view taken along line II--II in FIG. 1, and

FIG. 3 is a cross-sectional view taken along line III--III in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The total length of the electromagnetic track brake illustrated in thedrawings is chosen, within the limits set by the space available in theunderframe of a railway vehicle, according to the requirements as to thebraking capacity. However, in the drawing the brake is partly cut awayand is not shown in its full length, which normally may be of the orderof 1 meter.

The brake comprises an elongate energizing coil 1 of a slightlydifferent type than the one conventionally used in electromagnetic trackbrakes. It is enclosed by a substantially oval covering 2, which is onlyprotective and not force-transmitting and may be made of epoxy resin.The coil covering with the coil enclosed therein lies protected in aU-shaped bracket 3, mounted by screw connections 5 to the lower side ofa non-magnetic channel 4 open downwards.

Cables 6 for the electrical connection of the coil are extended from thecovering 2 through bushings 7 projecting from the upper side of thechannel 4, a gasket 8 being provided around each bushing between thecovering 2 and the channel 4.

U-shaped brackets 9 embrace the channel 4 and are connected to anglebars 21 described below but also to the channel by means of screws 10.In an opening 11 in the web of each bracket there is mounted by means ofscrew connections 12 a shock-absorbing bushing 13, and a suspension bolt14 is passed from below through the bushings 13 and is connectedtherewith by means of a nut 15 screwed onto the bolt. A bracket 16 isrigidly mounted to a journal box 17 --so as to follow the movements ofthe vehicle wheel--and has fixedly mounted thereto by screw connections18 a shock-absorbing bushing 19 of the same type as the bushing 13. Thebolt 14 is passed through the bushing 19 and is connected therewith bynuts 20 screwed onto the bolt. Thus, it will be seen that the coilcovering 2 is suspended from brackets 16 on two adjacent journal boxesof the vehicle and can be adjusted vertically by screwing the nuts 20 onthe bolts 14.

Inside the channel 4 angle bars 21 are connected to the brackets 9 bymeans of the screws 10, a damp insulating lining 22 being providedbetween the angle bars and the channel on the inner side of the channel.

These angle bars 21 serve as supporting means for the coil 1 with itscoil covering 2 and the channel 4.

The design so far described will see to it that the magnetic flux is notclosed in an "upper" loop, i.e.through the members 3, 4 or 21, 9.

A number of individual U-shaped braking shoes, each consisting of twolimbs 23 and a web 24 interconnected by screws 25, are mounted in a rowon the angle bars 21, said shoes being made of a ferromagnetic material.The mounting of the braking shoes is accomplished by means of bolts 26passing through bushings 27 in the angle bars 21 and screwed into theweb 24. Between each bushing 27 and the head 28 of the bolt 26, passingthrough the bushing, a helical pressure spring 29 is mounted to bias thebraking shoe in an upward direction. As will be seen, the web 24 of thebraking shoes thus mounted extends through the central aperture of theelongate coil covering 2, and the relationship between the dimensions ofthe web and the aperture are such that the individual shoes arevertically displaceable over a limited distance.

The limbs 23 of each braking shoe form braking surfaces 30 forco-operation with a rail fragmentarily indicated by dot and dash linesat 31. The limbs are mutually spaced by a gap, which is partly filled bya non-ferromagnetic material 32 in the portion thereof adjacent thesurfaces 30. A tie rod 33 extending from one end of the row of brakingshoes to the other end of said row is received by the open portion ofthe gap at a loose fit. This tie rod has rectangular cross section andforms a number of transverse flanges 34 projecting from opposite sidesof the tie rod and having a longitudinal spacing corresponding to thelength of the individual braking shoes 23, 24. The flanges 34 arereceived at loose fit in recesses 35 formed by the facing end surfacesof adjacent braking shoes as is seen in FIG. 3. At the ends the tie rodhas a head 36 of the same width as the braking shoe parts 23. An eye 38is screwed into the head 36.

A cylindrical rod 39 is adjustably fixed in a socket 40 by means of aset screw 41, said socket being of a sturdy construction and beingfixedly connected to the underframe 42 of the vehicle, e.g. by welding.The socket may also form an integral part of the underframe. The eye 38at each end of the row of braking shoes is passed onto the rod 39 whichthus forms means for anchoring the braking shoes to the underframe 42allowing vertical movement of the tie rod 33 together with the brakingshoes.

End walls 43 are welded to the angle bars 21, so that a sturdy frame 21,43 for the track brake is formed.

Normally, during operation of the vehicle, the braking shoes aremaintained in an upper position against the angle bars 21 under the biasof the pressure springs 29. In this position of the braking shoes, thebraking surfaces 30 are maintained rather closely spaced from the rail31, the space between the surfaces 30 and the rail 31 being determinedby the adjustment of the nuts 20.

When the brake described is to be engaged, the coil 1 is energized toproduce an electromagnetic flux which will flow in a closed path throughthe shoes 23, 24 and the rail 31, on which the vehicle runs. The brakingsurfaces 30 thus will be attracted to the rail and will frictionallyengage the rail surface. The braking reaction forces thus produced willbe transmitted from the row of braking shoes to the tie rod 33 over theflanges 34 and will be transmitted from the tie rod to the rod 39 on theunderframe 42 of the vehicle and thus will brake the vehicle. It will beseen that by the arrangement of the tie rod 33 operatively engaging thebraking shoes 23, 24, the bolts 14 and the connections between the boltsand the coil frame at the bushings 13 on one hand and between the boltsand the journal boxes at the bushings 19 on the other hand arecompletely relieved of the braking reaction forces.

We claim:
 1. An electromagnetic track brake to be mounted on a railwayvehicle for co-operation with a rail and comprising in combination, anelongate brake energizing coil having a lower disposed branch to bedisposed generally parallel to the rail, a rigid frame therefor, aplurality of generally U-shaped braking shoes mounted in a row in theframe around the lower branch of the coil and having braking surfacesdisposed beneath the coil for frictionally engaging the rail when thecoil is energized, means mounting each braking shoe individually movablein a vertical direction relative to the frame and lightly spring biasedupwards away from the rail towards a rest position, said track brakebeing mounted on a vehicle frame, a tie rod extending exteriorly alongthe lower branch of the coil, a covering therefor and engaging each ofthe braking shoes for the transmission of braking reaction forces fromthe shoes to the tie rod, and means rigid with the vehicle frame andoperatively connected to the end of said tie rod to take up the brakingreaction forces transmitted to the tie rod.
 2. A track brake accordingto claim 1, characterized in that said rigid means is so operativelyconnected to the tie rod that substantial vertical displacement of thetie rod is allowed.
 3. A track brake according to claim 2, characterizedin that said rigid means comprises a substantially vertical anchoringrod rigid with the vehicle frame, and that the tie rod has an eye at theend thereof, passed onto said anchoring rod and longitudinallydisplaceable thereon.
 4. A track brake according to claim 1,characterized in that the tie rod extends along the row of braking shoesin the gap formed between two limbs of the generally U-shaped brakingshoes.
 5. A track brake according to claim 4, characterized in that thetie rod has transverse members received between facing end surfaces ofadjacent braking shoes.
 6. A track brake according to claim 5,characterized in that said facing end surfaces of the braking shoes formrecesses receiving said transverse members of the tie rod.
 7. A trackbrake according to claim 5, characterized in that the transverse membersof the tie rod are integral with the tie rod.